1. Field of the Invention
The present invention relates to a range determination apparatus, a range determination method, and a program there for.
2. Description of the Related Art
In a conventional vehicle in which a gear ratio is changed by a transmission, for example, an automatic transmission such as a staged automatic transmission, a continuously variable transmission (CVT) or the like, responsive to range selection by operation of a shift lever, an automatic transmission control unit (ECU) switches a solenoid or the like on or off in accordance with a gearshift logic for the selected range and thereby controls gearshift of the transmission. For this purpose, the automatic transmission is provided with a range determination apparatus that receives an output signal from a sensor, determines a range on the basis of the output signal, and determines the selected range.
The sensor mentioned above may be a contact-type sensor having a movable-side terminal and a plurality of fixed-side terminals. The movable-side terminal is attached to a manual shaft that is turned by operation of the shift lever. The fixed-side terminals, with which the movable side terminal is in contact, are attached to a sensor case and provide sliding contact upon turning of the manual shaft. With this contact-type sensor, when the shift lever is operated to select a range, the movable-side terminal is turned via the manual shaft in accordance with the turning angle of the shift lever, whereby the pattern of contact between the movable-side terminal and the fixed-side terminals is changed. This causes a change in resistance in the electric circuit including the movable-side terminal and the fixed-side terminals. In accordance with this change in the contact pattern, the sensor generates an output signal corresponding to the turning angle of the manual shift, which output signal is either a voltage value or a current value.
Upon receiving the output signal from the contact-type sensor, the range determination apparatus compares the value of that output signal with thresholds as criteria for respective ranges, determines a range, and then determines the selected range. The thresholds (limits) are set in advance as voltage values or current values, depending on the type of the output signal (see U.S. Pat. No. 4,914,594).
However, in the aforementioned contact-type sensor and in the non-contact-type sensor of the related art, when the output value of the sensor is determined, the position of the shift lever is univocally determined, so that the selected range is unequivocally determined. In other words, only a single combination of thresholds for determining a range is set for a given output value of the sensor and a determination of range is made according to a single shift range determination pattern. Therefore, even if different control operations are performed in an automatic transmission control unit, only one item of range information can be obtained. In other words, optimal range information cannot be obtained for each of the various control operations.